A new method to evaluate soybeans for making tofu (soybean curd) is proposed. Dynamic viscoelasticity measurements were carried out to examine the gelation process of soymilk, storage and loss moduli being observed as a function of time after adding glucono-δ-lactone. The gelation curves fitted well with first-order reaction kinetics. The saturated value of the storage modulus correlated well with gel hardness by a curdmeter. The saturated value of the storage modulus was mainly dependent on the concentration of 11S globulin, while the gelation rate was an increasing function of the concentration of glucono-δ-lactone at a fixed 11S globulin concentration.